Originally Posted by
Oranoco
I would run the 6x9's off the headunit, and use the 4 channel amp to run front speakers and a sub as mentioned above by bridging 2 channels to give a single more powerfull channel for the sub (amp dependent as to this being possible). 6x9's aren't the best solution and amping them without doing anything to the fronts will give you noise but not a nice sound
This mans got it!
Sound from the back sounds nasty, get a decentish set of fronts and amp them leave the 6x9's for rear fill (if you have to have them) and it'll sound alot better.